As disclosed in the above-identified patent and application, there currently exists a need for small, compact self-contained pumps which may be mounted on or in the body and which are capable of delivering precisely controlled amounts of various active agents over prolonged periods of time. These devices exist in many forms such as disclosed in U.S. Pat. Nos. 4,320,757; 4,282,872; 3,731,681; and 3,469,578 and produce a significant improvement over the typical hypodermic injection in which a bolus of the active agent is deposited in the body either from conventional hypodermic injectors or specially designed injectors such as shown by U.S. Pat. No. 2,589,426. This bolus must then be gradually absorbed and distributed throughout the body which is a process subject to many individual variances, depending on the physiology of the individual patient. Thus, it is now recognized, particularly with extremely potent active agents such as insulin, interferon or various other chemotherapeutic agents, that it is preferable to have a continuous low rate of infusion of the active agent over a prolonged period of time such as 24 hours or longer rather than 3, 4 or more injections spaced within the same time period. Also, with certain active agents such as insulin, the requirements of the body vary according to conditions. A typical diabetic may have a requirement for a tonic or basal insulin level throughout the day, but after meals may require additional insulin to compensate for physiological changes caused by eating. Thus, a continuous infusion pump would preferably be provided with some means for imposing a pulse dosage on top of the tonic flow.
The infusion pumps disclosed in the above-identified patent and application, represent significant advances in the art since they are compact, reliable, dependable, and relatively inexpensive compared to other prior art devices. In working with such devices we have determined that the human as well as mechanical engineering factors of an infusion pump must be carefully considered in order to gain patient acceptance. These factors cover a wide spectrum of consideration. As discussed by Pickup, et al., "Patient Reaction to Long-term Out-patient Treatment with Continuous Subcutaneous Insulin Infusion" Br. Med. J., Volume 282, pp. 766-768, March 1981, the size of a pump and the psychological impact of wearing the pump on the patient's interpersonal relationships produced the most consistent adverse criticisms. Other factors which must be addressed in order to assure patient acceptance and compliance are ease of operation and handling, minimal adjustments in lifestyle and clothing, concealability, comfort, low cost, maintenance free operation, attractive appearance in use, compact size and ready confirmation of the status of the device i.e., filled, exhausted, pumping, not pumping, for example.
According to this invention, compact, light-weight, maintenance-free, concealable, highly stable and comfortable, easily operated and confirmable body-mounted pump assemblies are provided which are capable of dispensing both water-soluble and water-insoluble beneficial agents at a tonic flow rate or at a tonic flow rate with periodic pulses or with only periodic pulses. These pump assemblies comprise unique housings and unique arrangements of the pump components in combination with the housing and cannula.
It is accordingly an object of this invention to provide housings for body-mounted pump assemblies.
It is another object of this invention to provide body-mounted pump assemblies adapted to administer a pre-determined amount of active agent over a prolonged period of time.
It is another object of this invention to provide body-mounted pump assemblies capable of tonic and pulsed delivery.
It is another object of this invention to provide body mounted pump assemblies capable of administering pulsed doses of active agent.
It is another object of this invention to provide simple, inexpensive pump housings and pump assemblies capable of delivering both water soluble and water insoluble active agents.
It is another object of this invention to provide body mounted pumps whose operational status is visually confirmable.
It is another object of this invention to provide self-contained and self-actuated pump assemblies.
It is another object of this invention to provide pump assemblies with a cannula extending from the housing into the portion of the human body whereon the pump assembly is mounted.
It is another object of this invention to provide pump assemblies having a cannula extending from the housing at an angle which minimizes discomfort of insertion and retention.
It is another object of this invention to provide a pump assembly for delivering active agent to a portion of the human body distant from the mounting site of the pump assembly.
It is another object of this invention to provide pump assemblies with modular prefilled drug reservoirs.
It is another object of this invention to provide pump assemblies with reservoirs to be filled at or before the time of use.